1. Field of the Invention
The invention relates to a method of fabricating a display device and to the resulting display device and, more particularly, to a method of fabricating a display device equipped with organic electroluminescent devices (OEDs) and to the resulting display device.
2. Description of the Related Art
An organic electroluminescent device (OED) is composed of a lower electrode, an upper electrode, and organic layers sandwiched between the upper and lower electrodes. Each organic layer includes an emissive layer. OEDs have attracted attention as emissive devices capable of emitting high-intensity light with low-voltage DC drive.
An active-matrix-driven display device (i.e., an organic electroluminescent display) having such OEDs has thin-film transistors (TFTs) at each pixel on a substrate. OEDs constituting individual pixels are composed of a lower electrode patterned for each pixel and connected with the TFTs, organic layers formed on the lower electrode, and an upper electrode overlying the organic layers. Of these layers, the upper electrode is formed, for example, as a full-sized unpatterned film that covers plural pixels. The upper electrode is shared by plural pixels.
In such an active-matrix-driven display device, a sufficient level of aperture ratio can be effectively secured in the OEDs by constructing the device as a top emissive display. That is, light is taken out from the opposite side of the substrate.
A typical method of fabricating a top emissive display starts with preparing a TFT substrate made of an insulating material such as glass. OEDs are arranged on the display area of the substrate. Each OED is made of a lower electrode, an upper electrode, and organic layers sandwiched between the electrodes. External connector terminals are brought out from the OEDs and formed outside the display area on the substrate. Then, a protective film made, for example, of silicon nitride (SiNx) is formed over the whole area of the substrate under this condition by chemical vapor deposition (CVD). The protective film may also be formed from silicon oxide (SiO2) by the same CVD process.
Then, encapsulating resin is deposited over the protective film that is on the display area of the TFT substrate. Subsequently, a counter substrate made of an insulating material such as glass is placed opposite to the TFT substrate and aligned. The counter substrate is stuck to the TFT substrate such that the encapsulating resin is sandwiched between them. Subsequently, the encapsulating resin on the display area is cured, for example, by UV irradiation. The portions of the counter substrate which overlie the external terminal regions are removed by scribe dicing.
The portions of the protective film overlying the external terminal regions are then etched away by reactive ion etching (RIE) using NF3 gas. Thus, the surfaces of the external connector terminals are exposed.
There is a report on an example of forming the end surface of the protective film along the end surface of the counter substrate by etching the protective film by the RIE process using the counter substrate as a mask (see, for example, JP-A-2004-127637 (patent reference 1)).